Apparatus for physical vapor deposition and method for forming a layer

ABSTRACT

An apparatus for PVD is provided. The apparatus includes a chamber, a pedestal disposed in the chamber to accommodate a wafer, and a ring. The ring includes a ring body having a first top surface and a second top surface, and a barrier structure disposed between the first top surface and the second top surface. The barrier structure can further include at least a first portion and a second portion separated from each other. The second vertical distance is equal to or greater than the first vertical distance.

PRIORITY DATA

This patent claims the benefit of U.S. Provisional Patent Application Ser. No. 62/753,519 filed Oct. 31, 2018, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND

Physical vapor deposition (PVD) is a well-known process for depositing a thin film of material on a substrate and is commonly used in the fabrication of semiconductor devices. The PVD process is carried out at high vacuum in a chamber receiving a substrate (e.g., a wafer) and containing a solid source or slab of material to be deposited on the substrate. The solid source or the slab of material is therefore referred to as a PVD target. In the PVD process, the PVD target is physically converted from a solid into a vapor. The vapor of the target material is transported from the PVD target to the substrate where it is condensed on the substrate as a thin film.

There are many methods for accomplishing PVD including evaporation, e-beam evaporation, plasma spray deposition and sputtering. Presently, sputtering is the most frequently used method for accomplishing PVD. During the sputtering, plasma is created in the chamber and directed to the PVD target. The plasma physically dislodges or erodes (sputters) atoms or molecules from the reaction surface of the PVD target into a vapor of the target material, as a result of collision with high-energy particles (ions) of the plasma. The vapor of sputtered atoms or molecules of the target material is transported to the substrate through a region of reduced pressure and condenses on the substrate, forming the thin film of the target material.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic drawing illustrating an apparatus for PVD according to aspects of one or more embodiments of the present disclosure.

FIG. 2 is a schematic drawing illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure.

FIG. 3 is a schematic drawing illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure.

FIG. 4 is a schematic drawing illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure.

FIG. 5 is a schematic drawing illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure.

FIG. 6 is a schematic drawing illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure.

FIG. 7 is a schematic drawing illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure.

FIG. 8 is a schematic drawing illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure.

FIG. 9 is a schematic drawing illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure.

FIG. 10 is a schematic drawing illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure.

FIG. 11 is a flow diagram of a method for forming a layer in accordance with some embodiments of the present disclosure.

FIGS. 12A and 12B are schematic views of different stages in a method for forming a layer in accordance with some embodiments of the present disclosure.

FIG. 13 is an enlarged partial view of FIG. 12B.

FIG. 14 is a chart illustrating an electron density distribution during a PVD operation in the apparatus according to aspects of one or more embodiments of the present disclosure.

FIG. 15 is a chart illustrating an electron density distribution during a PVD operation in the apparatus according to aspects of one or more embodiments of the present disclosure.

FIG. 16 is a chart illustrating an electron density distribution during a PVD operation in the apparatus according to aspects of one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of elements and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” “on” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 100 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

As used herein, the terms such as “first,” “second” and “third” describe various elements, components, regions, layers and/or sections, but these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another. The terms such as “first,” “second” and “third” when used herein do not imply a sequence or order unless clearly indicated by the context.

PVD is an appropriate and widely-used process to form a thin film on a substrate (i.e., a wafer). Typically, the apparatus for performing a PVD operation includes a chamber and a process kit. The chamber may include a chamber wall and a pedestal, and the process kit may be placed within the chamber to prevent undesirable material deposition on the chamber components, such as the chamber wall and the pedestal.

Usually, the process kit includes a deposition ring. The deposition ring is disposed on the pedestal. A wafer may be disposed on the pedestal and an edge of the wafer may be above at least a portion of the deposition ring. During a PVD process for forming, for example but not limited to, a layer on the wafer, a problem recognized as arcing may occur. Arcing can be caused by factors such as contamination or residue over a surface of the wafer. It is found that the contamination or residues may cause local charge accumulation and thus serve as a potential arcing source. When a path is established from the wafer (i.e., where the residue exists) to the target through electrons or ions in the plasma, the arcing is caused. Arcing during PVD can cause a local thicker deposition of target material on the wafer. For example, an unwanted local thicker layer may be formed over a wafer edge.

In some comparative embodiments, extra cleaning operations may be performed to remove the residue, which serves as the potential arcing source, before the PVD operation. This approach may mitigate the arcing problem, but an overall throughput is reduced and process cost is increased. In other comparative embodiments, degassing time during the PVD operation is extended or a degassing temperature during the PVD operation is increased in order to mitigate the arcing problem, but the PVD operation throughput is reduced and energy consumption is increased. In still other comparative embodiments, discharge power is reduced in order to reduce charge accumulation, but this approach suffers from reduced PVD throughput. In summary, although apparatus designers have attempted to prevent arcing problem during PVD operation by making the above-mentioned modifications, none of these approaches can effectively reduce the arcing without increasing process time, energy consumption and cost, or without reducing the overall throughput.

The present disclosure therefore provides an apparatus for PVD to mitigate the arcing issue without reducing PVD throughput, increasing process cost, or increasing energy consumption. In some embodiments, a deposition ring including a barrier structure is provided. The barrier structure of the deposition ring is able to alter electron density distribution such that the path from the wafer (e.g., where the residue exists or the wafer edge) to the target through electrons or ions in the plasma may not be formed. Accordingly, arcing can be mitigated even though there is residue over the wafer.

FIG. 1 is a schematic drawing illustrating an apparatus for PVD 100 according to aspects of one or more embodiments of the present disclosure. It will be appreciated that although an apparatus is illustrated as having components specific for a PVD process, the aspects of the disclosed apparatus may be applied to any type of processing operation that utilizes plasma. For example, the disclosed aspects may be applied to a plasma-enhanced chemical vapor deposition (PECVD) operation or plasma etching operation.

Referring to FIG. 1, the apparatus for PVD 100 includes a chamber wall 102, a plasma source 104, a pedestal 110, a target 130 and a process kit 140 disposed within the chamber wall 102. The chamber wall 102 can be a stainless steel chamber body that is vacuum-tight, and a chamber 106 is enclosed within the chamber wall 102. The plasma source 104 is configured to provide plasma to the chamber 106. In some embodiments, the plasma source 104 may include an upstream source located external to the chamber 106, as shown in FIG. 1. In some alternative embodiments, the plasma source 104 can be located within the chamber 106. The pedestal 110, also referred to as wafer stage or a substrate support, is disposed within the chamber wall 102 for supporting and accommodating a workpiece, such as a wafer, to be processed. In some embodiments, the pedestal 110 may include an electrostatic chuck (ESC) 112 and/or a heater (not shown). In some embodiments, an RF bias power source 114 may be coupled to the pedestal 110 in order to induce a negative DC bias on the workpiece. In other embodiments, the pedestal 110 may be grounded or left electrically floating. In some embodiments, the apparatus for PVD 100 further includes a communication interface (not shown), for example, a monitor, showing the required operation parameters of the current deposition operation.

Referring to FIG. 1, the target 130 may have a sputtering surface. A power supply 132 can be electrically connected to the target 130. In various embodiments of the present disclosure, the power supply 132 is a DC supply, an RF power supply, or a DC-RF power supply. The target 130 is posed of metal or metal alloys which are predetermined to be deposited onto the wafer 120. The target 130 may be composed of any suitable and appropriate source material including, for example but not limited thereto, nickel (Ni), nickel platinum (Ni Pt) alloys, nickel titanium (Ni Ti) alloys, cobalt (Co), aluminum (Al), copper (Cu), titanium (Ti), tantalum (Ta), tungsten (W), indium tin oxide (ITO), zinc sulfide-silicon dioxide (ZnS—SiO₂), gold (Au), silver (Ag) and other noble metals.

Still referring to FIG. 1, the process kit 140 may be placed within the chamber wall 102 to prevent material from being deposited on the chamber components, such as the chamber wall 102 and the pedestal 110. Specifically, the process kit 140 includes a first ring 150 or 151, a second ring 160 and a wall shield 170. In some embodiments, the first ring 150 or 151 can be a deposition ring 150/151 and may include an annular band surrounding the pedestal 110. The second ring 160, such as a cover ring 160, also referred to as a clamp ring, may at least partially cover the deposition ring 150. In some embodiments, the cover ring 160 holds the wafer 120 in place on the pedestal 110 when a positive gas pressure is applied between the heater and the pedestal 110 such that heat can be efficiently conducted from the heater to the wafer 120. Another function served by the cover ring 160 is to allow a predetermined flow of argon to leak from under the wafer 120 into the chamber 106. The cover ring 160 is constructed with an annular shape with an oriented cut-out to match a wafer's flat side. As shown in FIG. 1, the wall shield 170 forms a seal between the cover ring 160 and the chamber wall 102 to reduce the contamination of the chamber wall 102 resulting from the particles sputtered from the target 130.

The wall shield 170 helps to prevent or minimize depositing of target material films on the interior surfaces of the chamber wall 102. The wall shield 170 may include an annular attachment portion which is mounted to the chamber wall 102, an annular vertical portion which extends downwardly from the attachment portion; and an annular horizontal portion which extends inwardly from the vertical portion.

As shown in FIG. 1, the deposition ring 150 or 151 can be disposed on the pedestal 110 and may be at least partially covered by the cover ring 160.

Please refer to FIGS. 2 to 5, which are schematic drawings illustrating a deposition ring according to aspects of one or more embodiments of the present disclosure. As shown in FIGS. 2 and 3, the deposition ring 150 includes a ring body 152 having a first top surface 154 a and a second top surface 154 b, and a barrier structure 156 disposed between the first top surface 154 a and the second top surface 154 b. In some embodiments, an innermost surface 153 of the ring body 152, which is an annular surface, may be in contact with electrostatic chuck (ESC) 112 or pedestal 110, but the disclosure is not limited thereto. In some embodiments, the first top surface 154 a is an annular surface coupled to the innermost surface 153, the barrier structure 156 is an annular structure surrounding the first top surface 154 a, and the second top surface 154 b is an annular surface surrounding the first top surface 154 a and the barrier structure 156. In some embodiments, the ring body 152 and the barrier structure 156 are monolithic. In some embodiments, the ring body 152 and the barrier structure 156 include a same material, such as a conductive material. For example but not limited thereto, the ring body 152 and the barrier structure 156 may include stainless steel, but the disclosure is not limited thereto. In some embodiments, an insulating film 158 is disposed over the barrier structure 156, as shown in FIG. 3. In some embodiments, the insulating film 158 includes aluminum oxide (Al_(X)O_(Y)) or aluminum nitride (Al_(X)N_(Y)), but the disclosure is not limited thereto. Additionally, a bottom of the ring body 152 may have a step height, as shown in FIG. 2, in order to help to secure the ring body 152 over the pedestal 110, but the disclosure is not limited thereto. In other embodiments, the bottom of the ring body 152 can have a flat surface, though not shown.

The barrier structure 156 is separated from the first top surface 154 a by a horizontal distance D_(H), which is defined between a vertical sidewall of the barrier structure 156 that faces the first top surface 154 a and a vertical wall of the ring body 152 that is coupled to the first top surface 154 a and faces the barrier structure 156, as shown in FIG. 2. In other embodiments, when the barrier structure 156 includes the insulating film 158, the horizontal distance D_(H) is defined between a vertical surface of the insulating film 158 that faces the first top surface 154 a and the vertical wall of the ring body 152 that is coupled to the first top surface 154 a and faces the barrier structure 156, as shown in FIGS. 3 to 5. In some embodiments, the horizontal distance D_(H) is greater than 0.

As shown in FIGS. 2 to 5, in some embodiments, a first vertical distance D_(V1) is defined between a top surface of the barrier structure 156 and the first top surface 154 a of the ring body 152, and a second vertical distance D_(V2) is defined between the top surface of the barrier structure 156 and the second top surface 154 b of the ring body 152, as shown in FIG. 2. In some embodiments, when the barrier structure 156 includes the insulating film 158, the top surface is a surface of the insulating film 158. Accordingly, the first vertical distance D_(V1) is defined between the top surface of the insulating film 158 of the barrier structure 156 and the first top surface 154 a of the ring body 152, and the second vertical distance D_(V2) is defined between the top surface of the insulating film 158 of the barrier structure 156 and the second top surface 154 b of the ring body 152, as shown in FIGS. 3 to 5.

In some embodiments, the first top surface 154 a and the second top surface 154 b of the ring body 152 are not coplanar with each other. For example, the first top surface 154 a is higher than the second top surface 154 b, as shown in FIGS. 2 and 3. In some embodiments, the first vertical distance D_(V1) and the second vertical distance D_(V2) are different from each other, as shown in FIGS. 2 and 3. In some embodiments, both of the first and second vertical distances D_(V1) and D_(V2) are greater than 0, and the second vertical distance D_(V2) is greater than the first vertical distance D_(V1), as shown in FIGS. 2 and 3. In addition, a groove 159 may be disposed between the barrier structure 156 and the first top surface 154 a. Shapes of the barrier structure 156 or the groove 159 can be modified. The modified shapes are also included in the scope of the present disclosure.

In some embodiments, the first top surface 154 a and the second top surface 154 b of the ring body 152 are coplanar with each other, as shown in FIG. 4. In some embodiments, the first vertical distance D_(V1) and the second vertical distance D_(V2) are the same, as shown in FIG. 4. In such embodiments, both of the first and second vertical distances D_(V1) and D_(V2) are greater than 0. In addition, a groove 159 may be disposed between the barrier structure 156 and the first top surface 154 a. Shapes of the barrier structure 156 or the groove 159 can be modified. The modified shapes are also included in the scope of the present disclosure.

Referring to FIG. 5, in some embodiments, the first top surface 154 a and the second top surface 154 b of the ring body 152 are not coplanar with each other. For example, the first top surface 154 a is higher than the second top surface 154 b, as shown in FIG. 5. In some embodiments, the top surface of the barrier structure 156 or the top surface of the insulating film 158 is coplanar with the first top surface 154 a of the ring body 154 a. Therefore the first vertical distance D_(V1) is equal to 0. In such embodiments, the first vertical distance D_(V1) and the second vertical distance D_(V2) are different from each other. As shown in FIG. 5, the second vertical distance D_(V2) is greater than the first vertical distance D_(V1).

Referring to FIGS. 6 to 10, in some embodiments, the process kit 140 can include a deposition ring 151. As shown in FIGS. 6 to 10, the deposition ring 151 includes a ring body 152 having a first top surface 154 a and a second top surface 154 b, and a barrier structure 156 a, 156 b disposed between the first top surface 154 a and the second top surface 154 b. In some embodiments, the barrier structure includes at least a first portion 156 a and a second portion 156 b. In other embodiments, the barrier structure 156 a, 156 b can include more than two portions. In some embodiments, the first top surface 154 a is an annular surface, the first portion 156 a of the barrier structure is an annular portion surrounding the first top surface 154 a, the second portion 156 b of the barrier structure is an annular portion surrounding the first portion 156 a, and the second top surface 154 b is an annular surface surrounding the first top surface 154 a and the barrier structure 156 a, 156 b. In some embodiments, the ring body 152 and the barrier structure 156 a, 156 b are monolithic. In some embodiments, the ring body 152 and the barrier structure 156 a, 156 b include a same material, such as a conductive material. For example but not limited thereto, the ring body 152 and the barrier structure 156 a, 156 b may include stainless steel, as shown in FIGS. 6 to 10, but the disclosure is not limited thereto. In some embodiments, an insulating film 158 is disposed on the first portion 156 a and the second portion 156 b of the barrier structure, as shown in FIGS. 7 to 10. In some embodiments, the insulating film 158 includes Al_(X)O_(Y) or Al_(X)N_(Y), but the disclosure is not limited thereto. It should be noted that in some embodiments, the insulating film 158 is disposed or coated on both of the first portion 156 a and the second portion 156 b, as shown in FIGS. 7 to 10. In other embodiments, the insulating film 158 can be disposed on the first portion 156 a only. In still other embodiments, the insulating film 158 can be disposed on the second portion 156 b, only.

In some embodiments, the first portion 156 a and the second portion 156 b are separated from each other by a first horizontal distance D_(Ha), which is defined by a vertical sidewall of the first portion 156 a that faces the second portion 156 b and a vertical sidewall of the second portion 156 b that faces the first portion 156 a, as shown in FIG. 6. Further, the first top surface 154 a of the ring body 152 and the first portion 156 a of the barrier structure are separated by a second horizontal distance D_(Hb), which is defined between the vertical sidewall of the first portion 156 a that faces the first top surface 154 a and a vertical wall of the ring body 152 that is coupled to the first top surface 154 a and faces the first portion 156 a, shown in FIG. 6. In some embodiments, when the first portion 156 a and the second portion 156 b include the insulating film 158, the first horizontal distance D_(Ha) is defined between a vertical surface of the insulating film 158 on the first portion 156 a that faces the second portion 156 b and a vertical surface of the insulating film 158 on the second portion 156 b that faces the first portion 156 a, as shown in FIGS. 7 to 10. Further, the second horizontal distance D_(Hb), is defined between the vertical surface of the insulating film 158 on the first portion 156 a (and facing the first top surface 154 a) and the vertical wall of the ring body 152 that is coupled to the first top surface 154 a (and faces the first portion 156 a), as shown in FIGS. 7 to 10. Both of the first horizontal distance D_(Ha) and the second horizontal distance D_(Hb) are greater than 0. In some embodiments, the first horizontal distance D_(Ha) and the second horizontal distance D_(Hb) are the same.

As shown in FIG. 6, in some embodiments, a first vertical distance D_(Va) is defined between a top surface of the first portion 156 a and a top surface of the second portion 156 b, a second vertical distance D_(Vb) is defined between the first top surface 154 a of the ring body 152 and the top surface of the first portion 156 a of the barrier structure, and a third vertical distance D_(Vc) is defined between the first top surface 154 a of the ring body 152 and the top surface of the second portion 156 b of the barrier structure. The third vertical distance D_(Vc) can be a sum of the first vertical distance D_(Va) and the second vertical distance D_(Vb). In some embodiments, when the first portion 156 a and the second portion 156 b of the barrier structure 156 include the insulating film 158, the top surface is a surface of the insulating film 158, as shown in FIGS. 7 to 10. Accordingly, the first vertical distance D_(Va) is defined between the top surface of the insulating film 158 on the first portion 156 a and the top surface of the insulating film 158 on the second portion 156 b, the second vertical distance D_(Vb) is defined between the top surface of the insulating film 158 on the first portion 156 a and the first top surface 154 a of the ring body 152, and the third vertical distance D_(Vc) is defined between the insulating film 158 on the second portion 156 b of the barrier structure and the first top surface 154 a of the ring body 152, as shown in FIGS. 7 to 10.

In some embodiments, the first top surface 154 a and the second top surface 154 b are not coplanar with each other. For example, the first top surface 154 a is higher than the second top surface 154 b, as shown in FIGS. 6 to 8. In some embodiments, the first vertical distance D_(Va) and the second vertical distance D_(Vb) are the same, as shown in FIGS. 6 and 7. In other embodiments, the first vertical distance D_(Va) and the second vertical distance D_(Vb) are different from each other. For example, the second vertical distance D_(Vb) is greater than the first vertical distance D_(Va), as shown in FIG. 8. In still other embodiments, the second vertical distance D_(Vb) can be less than the first vertical distance D_(Va), though such arrangement is not shown. In some embodiments, both of the first and second vertical distances D_(Va) and D_(Vb) are greater than 0, as shown in FIGS. 6 to 8. In addition, a groove 159 a may be disposed between the first portion 156 a and the second portion 156 b, and a groove 159 b may be disposed between the first portion 156 a and the first top surface 154 a. Shapes of the first portion 156 a and the second portion 156 b of the barrier structure or the grooves 159 a and 159 b can be modified. The modified shapes are also included in a scope of the present disclosure.

In some embodiments, the first top surface 154 a and the second top surface 154 b are flush with each other, as shown in FIGS. 9 and 10. In some embodiments, the first vertical distance D_(Va) and the second vertical distance D_(Vb) are the same, as shown in FIG. 9. In other embodiments, the first vertical distance D_(Va) is greater than the second vertical distance D_(Vb), as shown in FIG. 10. In still other embodiments, the second vertical distance D_(Vb) can be greater than the first vertical distance D_(Va), though such arrangement is not shown.

Please refer to FIGS. 11 to 13, wherein FIG. 11 is a flow diagram of a method for forming a layer in accordance with some embodiments of the present disclosure, FIGS. 12A and 12B are schematic views of different stages in a method for forming a layer in accordance with some embodiments of the present disclosure, and FIG. 13 is an enlarged partial view of FIG. 12B. In some embodiments, a method for forming a layer 20 is provided. The method 20 can include operations 202, 204 and 206.

Referring to FIG. 12A, in some embodiments, in operation 202, a workpiece such as a wafer 120 is received in an apparatus for deposition, such as the abovementioned apparatus for PVD 100. The wafer 120 can be positioned in the chamber 106 through a wafer port (not shown). In some embodiments, the wafer 120, being placed on the pedestal 110 is raised to an operation position with the heater touching the cover ring 160 of the process kit 140 as shown in FIG. 12B. In some embodiments, a bottom surface of the wafer 120 may be in contact with the first top surface 154 a of the ring body 152 of the deposition ring 150, as shown in FIG. 13. It should be noted that although the deposition ring 150 is illustrated in FIGS. 12A, 12B and 13, those skilled in that art would easily realize that the deposition ring 151 can be used in some embodiments, though not shown.

Referring to FIGS. 12B and 13, in operation 204, the target 130 is sputtered. As mentioned above, the target 130 is posed of metal or metal alloys which are predetermined to be deposited onto the wafer 120. In some embodiments, a plasma may be introduced to impact the surface of the target 130, which may be electrically biased by the power supply 132. Atoms, molecules and/or ions may be generated from the target 130. In some embodiments, a pressure within the chamber 106 is adjusted to a desirable pressure. A reactant gas such as argon (Ar) or nitrogen (Ni) is introduced into the chamber 106 until an optimum condition for igniting plasma is reached and the plasma source 104 can be turned on to ignite the plasma. Ions, such as Ar or N ions in the plasma, are accelerated and the target 130 is struck by the ions. Consequently, the target 130 is sputtered and the sputtered material is deposited onto a top surface of the wafer 120 to form a layer in operation 206. In operations 204 and 206, the barrier structure 156 may alter election density distribution during the depositing the sputter material, which will be described in FIGS. 14-16.

Still referring to FIG. 13, in some embodiments, a horizontal distance D_(HW) defined by an edge of the wafer 120 and the barrier structure 154, is between approximately 0.01 mm and approximately 10 mm. In some comparative embodiments, when the horizontal distance D_(HW) is less than 0.01 mm, the barrier structure 156 may be too close to the edge of the wafer 120 to alter election density distribution. In some comparative embodiments, when the horizontal distance D_(HW) is greater than 10 mm, the alteration provided by the barrier structure 156 may be too far from the wafer 120 to make sufficient difference. In some embodiments, a vertical distance D_(VW), defined by a top surface of the barrier structure 156 and a top surface of the wafer 120 is between approximately 0 mm and approximately 50 mm. In some embodiments, the top surface of the barrier structure 156 can be higher than the top surface of the wafer 120. In other embodiments, the top surface of the barrier structure 156 can be lower than the top surface of the wafer 120. Therefore, the vertical distance D_(VW) between the top surface of the barrier structure 156 and the top surface of the wafer 120 can be between approximately 0 mm and approximately 50 mm. In some comparative embodiments, when the vertical distance between the top surface of the barrier structure 156 and the top surface of the wafer 120 is greater than 50 nm, the barrier structure 156 may fail to alter election density distribution. In some comparative embodiments, when the vertical distance between the top surface of the barrier structure 156 and the top surface of the wafer 120 is greater than 50 nm, the barrier structure 156 may obstruct material deposition. In some embodiments, when the insulating film 158 is coated on the barrier structure 156 (including the first portion 156 a and/or the second portion 156 b), the vertical distance D_(VW) can be defined by a top surface of the insulating film 158 and the top surface of the wafer 120, and the distance between the top surface of the insulating film 158 and the top surface of the wafer 120 can be between approximately −50 mm and approximately 50 mm, but the disclosure is not limited thereto.

FIG. 14 is a chart illustrating an election density distribution during a PVD operation in the apparatus 100 according to aspects of one or more embodiments of the present disclosure. It should be noted that the insulating film 158 is omitted from FIG. 14 for the purpose of clarity. In some comparative embodiments, in which no barrier structure 156 is adopted, the electron density around the wafer edge may be greater than 0.5×10¹⁵ m⁻³. In some embodiments, in which the barrier structure 156 having the top surface coplanar with the first top surface 154 a of the ring body 152 is adopted, the electron density distribution in the plasma is altered. Additionally, the top surface of the barrier structure 156 is lower than the top surface of the wafer 120. For example, the electron density around the wafer edge may be reduced from 0.5×10¹⁵ m⁻³ to less than 0.3×10¹⁵ m⁻³, but the disclosure is not limited thereto. In some embodiments, the electron density around the wafer edge is reduced by more than 20%, but the disclosure is not limited thereto. Significantly, because the electron density is reduced, an incidence rate of arcing is reduced.

FIG. 15 is a chart illustrating an electron density distribution during a PVD operation in the apparatus 100 according to aspects of one or more embodiments of the present disclosure. It should be noted that the insulating film 158 is omitted from FIG. 15 for the purpose of clarity. In some comparative embodiments, in which no barrier structure 156 is adopted, the electron density around the wafer edge may be greater than 0.5×10¹⁵ m⁻³. In some embodiments, in which the barrier structure 156 having the top surface higher than the first top surface 154 a is adopted, the electron density distribution in the plasma is altered. Additionally, the top surface of the barrier structure 156 is higher than the top surface of the wafer 120. For example, the electron density around the wafer edge may be reduced from 0.5×10¹⁵ m⁻³ to less than 0.3×10¹⁵ m⁻³, but the disclosure is not limited thereto. It can be found that a portion of the plasma with greater electron density (e.g., electron density greater than 0.3×10¹⁵ m⁻³) is pushed away from the wafer edge. In some embodiments, the electron density around the wafer edge is reduced by more than 30%, but the disclosure is not limited thereto. Significantly, because the electron density is reduced, an incidence rate of arcing is reduced.

FIG. 16 is a chart illustrating an electron density distribution during a PVD operation in the apparatus 100 according to aspects of one or more embodiments of the present disclosure. It should be noted that the insulating film 158 is omitted from FIG. 16 for the purpose of clarity. As mentioned above, in some comparative embodiment in which no barrier structure is adopted, the electron density around the wafer edge may be greater than 0.5×10¹⁵ m⁻³. In some embodiments, when the barrier structure including the first portion 156 a and the second portion 156 b is adopted, the electron density distribution in the plasma is altered. For example, the electron density around the wafer edge may be reduced from 0.5×10¹⁵ m⁻³ to less than 0.3×10¹⁵ m⁻³, but the disclosure is not limited thereto. It can be found that a portion of the plasma with greater electron density (e.g., electron density greater than 0.3×10¹⁵ m⁻³) is pushed away from the wafer edge by the first portion 156 a and the second portion 156 b. In some embodiments, the electron density around the wafer edge is reduced by more than 30%, but the disclosure is not limited thereto. Significantly, because the electron density is reduced, an incidence rate of arcing is reduced.

As shown in FIGS. 14 to 16, because the electron density distribution of the plasma is altered by the barrier structure 156 of the deposition ring 150 or the barrier structure (i.e., the first portion 156 a and the second portion 156 b) of the deposition ring 151, the electron density around the wafer edge is reduced and thus the incidence rate of arcing is reduced. Consequently, the arcing issue is mitigated.

Accordingly, there is no need to adjust the PVD operation or parameters in order to avoid the arcing issue. In other words, the operation is simplified. Further, the arcing issue can be mitigated without reducing PVD throughput or increasing energy consumption. In some embodiments, because the deposition rings 150 and 151 effectively mitigate the arcing issue, additional cleaning processes for removing the residue over the wafer 120 can be omitted, and thus the overall throughput can be increased and process cost can be reduced.

The present disclosure provides an apparatus for PVD to mitigate the arcing issue without reducing PVD throughput, increasing process cost, or increasing energy consumption. In some embodiments, a deposition ring including a barrier structure is provided. The barrier structure of the deposition ring is able to alter the electron density distribution and thus electron density of the plasma around the wafer edge is reduced. Accordingly, incidence rate of arcing can be reduced. In other words, the arcing issue is mitigated although there still is residue over the wafer edge.

In some embodiments, a ring is provided. The ring includes a ring body having a first top surface and a second top surface, and a barrier structure disposed between the first top surface and the second top surface. In some embodiments, the barrier structure is separated from the first top surface by a horizontal distance. A first vertical distance is defined between the barrier structure and the first top surface, and a second vertical distance is defined between the barrier structure and the second top surface. In some embodiments, the second vertical distance is equal to or greater than the first vertical distance.

In some embodiments, an apparatus for PVD is provided. The apparatus includes a chamber, a pedestal disposed in the chamber to accommodate a wafer, and a ring. The ring includes a ring body having a first top surface and a second top surface, and a barrier structure disposed between the first top surface and the second top surface.

In some embodiments, a method for forming a layer is provided. The method includes following operations. A workpiece is received in an apparatus for deposition. In some embodiments, the apparatus for deposition includes a chamber, a pedestal disposed in the chamber to accommodate the workpiece, and a ring disposed on the pedestal. The ring includes a ring body having a first top surface and a second top surface and a barrier structure disposed between the first top surface and the second top surface. A vertical distance is defined by a top surface of the barrier structure and a top surface of the workpiece. In some embodiments, the vertical distance is between approximately 0 mm and approximately 50 mm. A target disposed in the apparatus for deposition is sputtered. A sputtered material is deposited onto a top surface of the workpiece to form a layer. In some embodiments, the barrier structure alters an electrical density distribution during the depositing the sputter material.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A ring, comprising: a ring body having a first top surface and a second top surface; and a barrier structure disposed between the first top surface and the second top surface, wherein the barrier structure is separated from the first top surface by a horizontal distance, a first vertical distance is defined between the barrier structure and the first top surface, a second vertical distance is defined between the barrier structure and the second top surface, and the second vertical distance is equal to or greater than the first vertical distance.
 2. The ring of claim 1, wherein the first top surface has an annular shape, the barrier structure has an annular structure surrounding the first top surface, and the second top surface has an annular surface surrounding the first top surface and the barrier structure.
 3. The ring of claim 1, wherein the ring body and the barrier structure comprise a conductive material.
 4. The ring of claim 3, further comprising an insulating film disposed over the barrier structure.
 5. The ring of claim 1, wherein the first vertical distance and the second vertical distance are substantially the same.
 6. The ring of claim 1, wherein the first vertical distance and the second vertical distance are substantially different from each other.
 7. A ring, comprising: a ring body having a first top surface and a second top surface; and a barrier structure disposed between the first top surface and the second top surface, wherein the barrier structure comprises at least a first portion and a second portion, the first portion and the second portion are separated by a first horizontal distance, and a first vertical distance is defined between the first portion and the second portion.
 8. The ring of claim 7, wherein the first top surface is an annular surface, the first portion of the barrier structure is an annular portion surrounding the first top surface, the second portion of the barrier structure is an annular portion surrounding the first portion, and the second top surface is an annular surface surrounding the first top surface and the barrier structure.
 9. The ring of claim 7, wherein the first top surface and the first portion of the barrier structure are separated by a second horizontal distance.
 10. The ring of claim 9, wherein the first horizontal distance and the second horizontal distance are the same.
 11. The ring of claim 7, wherein a second vertical distance is defined between the first top surface and the first portion of the barrier structure.
 12. The ring of claim 11, wherein the first vertical distance and the second vertical distance are the same.
 13. The ring of claim 11, wherein the first vertical distance and the second vertical distance are different.
 14. The ring of claim 7, wherein the ring body and the barrier structure comprises a conductive material.
 15. The ring of claim 14, further comprising an insulating film disposed on the barrier structure.
 16. A method for forming a layer, comprising: receiving a workpiece in an apparatus for deposition, wherein the apparatus for deposition comprises a chamber, a pedestal disposed in the chamber to accommodate the workpiece and a ring disposed on the pedestal; sputtering a target disposed in the apparatus for deposition; and depositing a sputtered material onto a top surface of the workpiece to form a layer, wherein the ring comprises a ring body having a first top surface and a second top surface, and a barrier structure disposed between the first top surface and the second top surface, a vertical distance is defined by a top surface of the barrier structure and a top surface of the workpiece, the vertical distance is between approximately 0 mm and approximately 50 mm, and the barrier structure alters an electrical density distribution during the depositing the sputter material.
 17. The method of claim 16, wherein a horizontal distance is defined by an edge of the workpiece and the barrier structure, and the horizontal distance is between approximately 0.01 mm and approximately 10 mm.
 18. The method of claim 16, wherein the top surface of the barrier structure is higher or lower than the top surface of the workpiece.
 19. The method of claim 16, wherein the ring body and the barrier structure include conductive material.
 20. The method of claim 19, further comprising an insulating film disposed on the barrier structure. 